如何检测input框里面输入的全是数字

首先我们封装一个函数用来检测字符串是不是全是数字

                             functino detectNum(str){

                      var n=0;

                                   for(var i=0;i<str.length;i++){                 

                          n= str.charCodeAt(i)

                        if(n<48||N>57){

                                   return false;

                         }

                         return turn;

                     }

}

然后我们做一个例子

                       <input type='button' />

                 <input type='text'  />

                               <script>

                              var oInput=document.getElementByTagName('input');

                               oInput[0].onclick=function(){

                                if(detectNum(oInput[1].value)){

                               alert('恭喜你输入的为数字')

}  else{

                                alert('输入有误')

}

                                }

                   </script>